DE2544660A1 - METHOD FOR AUTOMATIC EXPOSURE CONTROL AND DEVICE FOR CARRYING OUT THE METHOD - Google Patents

Description

PATENT ADVOCATE A. GRUNECKER

DlPL-ING

H. KINKELDEY

DH-ING.

W. STOCKMAIR

DR.HMCi · anE (CALTECH

K. SCHUMANN

Since RER MAX ■ UPL-PHVS

P. H. JAKOB

DtPU-tr-üJ

G. BEZOLD

OR RBlNAf-CWL-CHEM

MUNICH E. K. WEiL

UNDAU MUNICH 22

MAXIMILIANSTRASSE 43

October 6, 1975

ASAHI KOGAKU KOG-YO KABUSHIKI KAISHA PH 9655

ITo. 36-9, Maeno-cho, 2-chome "Ita" bashi-ku, Tokyo, Japan

Automatic reporting control method and device to carry out the procedure

The invention relates to a method for automatic exposure control for a camera with a lens system, a film transport system that holds a film with a certain film speed contains, with a shutter system that opens and closes the shutter with a variable shutter speed a movable 31end for determining the area of the lens system during actuation of the shutter, and with one Light measuring arrangement for measuring the brightness of the object of the camera, the 31 end by means of the light measuring arrangement in the

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TEUEFON (Ο89) 22 28 82 TELEX OS-2938Ο TELEGRAMS MONAPAT

Way is controlled that the time after the start of the movement of the diaphragm, the light measuring device automatically stops the movement of the Aperture in the appropriate position for the correct film exposure depending on the film speed, the shutter speed and the brightness of the object ended.

The invention also relates to a device for automatic Exposure control in a single lens reflex camera with a movable aperture, with a shutter with variable Shutter speeds, and with a film transport system containing a film of known film speed,

In general, the present invention relates to single lens reflex cameras with automatic exposure control, wherein Information about the brightness of the object to be recorded is stored and the aperture automatically by means of a electromagnetic mechanism is controlled. In particular, an iris diaphragm is used.

Various measuring systems have been proposed to measure the aperture value the camera automatically depending on the brightness to control the property. However, the disadvantages of these measuring devices are generally that they only have a low mechanical and have electrical strength and reliability. Furthermore The meter is also used as a light meter, so that it can be used in relation to the occupied space or the other systems Operation is inferior in interaction with the other parts. Furthermore, in a balance system, the * must have a servo motor used the engine to be relatively powerful; However, it is difficult to accommodate such a motor in a camera so that the camera still has a compact structure.

Used to control the aperture of a shutter-advance system is used, time itself is the

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output signal; if the APEX system is used, the result is

the following relationship: if the brightness value (Bv) changes in 3 steps, the time value or time value (Tv) changes in 3 steps, although it is one value

3
which is proportional to 2.

When the time is in an exponential relationship to the brightness value and if the lens has an aperture value of 1.4 to 22 (8 stops) and if 1 ms is required to adjust the setting

to be carried out on P2 (1 step), then 1x2 = 256 ms are required, to make the setting on P22. For example, must The amount of light has been adjusted for single-lens reflex cameras be before the shutter is operated; therefore, a relatively long period of time is required for this adjustment, so that not only the opportunity is missed at which the shutter is to be released, but also affects the stability of the recording will. For these reasons, it is not advisable to control the opening time by means of a locking system .

The invention is therefore based on the object of creating a method of the specified type in which this disadvantage does not occur occurs.

According to the invention, this object is achieved in a method as specified Genus solved in that a linear relationship is established between the value for the brightness of the object and the period of time becomes ^ which is required from the beginning of the movement of the diaphragm until the end of this movement.

In a device of the kind mentioned above, this object is achieved by a timing circuit which is triggered at the start of movement of the shutter to a blocking device for the diaphragm movement, an external control signal in the W _e supplying ise that the brightness value in a linear relationship to the amount of time stands between the start of the movement of the diaphragm and the external control signal for the locking device.

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The advantages achieved with the invention are in particular that an automatic exposure control is created which is particularly suitable for a single-lens reflex camera. This system uses an electromagnet to stop the shutter from moving from a preset value to the exact exposure value for the required image. An electronic switch, which is actuated in a specific time relation to the brightness value of the object to be photographed, controls the movement of the solenoid. This time relationship is linear and not exponential, so that the time required to adjust the lens to a bright scene (F22) is of the order of 8 ms instead of 256 ms. As a result, the sequence of movements of the shutter can be carried out quickly after the shutter is released by hand, with only a short delay being required for the automatic exposure control. This allows more precisely by the photographers the absorption and better adjusted and positioned, which is essential especially for images with fast-moving images or very short exposure times.

The invention thus provides a method and an apparatus to automatically control the diaphragm or iris in a camera, with a linear relationship between the movement of the lens diaphragm and the brightness value of the scene to be recorded with the camera, the shutter speed and the film value or film speed consists.

The invention is described below on the basis of exemplary embodiments with reference to the accompanying schematic drawings explained in more detail.

Show it:

1 shows the electrical circuit arrangement of the preferred embodiment of the time switch and switchover device the exposure control system; and

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Fig. 2 is a perspective view of the electromechanical device for opening or shutter control according to the present invention.

As can be seen from Fig. 1, there is a photo element 1 and a logarithmic one Conversion or conversion performing: diodes 2, 3 connected in series with an energy source 16; to a connection point a ^ between these elements are a storage capacitor 5 and an operational amplifier 6 with a high input impedance connected by a memory switch 4, which the storage time certainly. The operational amplifier 6 acts as a voltage follower switched, i.e. its output signal is fed back to an input.

A variable resistor 7 and a logarithmic conversion or Performing forming ;. Diodes 8,9 are in series with the energy source 16 switched; at a connection point b_ between them An operational amplifier 10 with a high input impedance is connected to elements. The operational amplifier 10 is also as Voltage follower switched, i.e. its output signal is on a Input fed back.

A reset switch is parallel to an integration capacitor 11 12 switched; one connection of the integration capacitor 11 is through a constant current source 13 with the power source connected, while the other connection is connected to the output of the Opera-: tion amplifier 10 is connected. A connection point d_ between the constant current source 13 and the capacitor 11 is connected to the non-reversible input of an operational amplifier 14 connected, while the output of the operational amplifier 6 with the reversible input of the operational amplifier 14 is connected. The operational amplifier 14 is designed as a switching arrangement; its output is connected to the excitation winding of an electromagnet 15 to stop the movement of the diaphragm.

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The operation of the circuit is described below will. When the terminal voltage and the resistance value of the photoconductive element or photo element represented by V and E, respectively, is the current i in the Conversion diodes 2 and 3 by the following. Given equation:

I ₁ = V ₁ / R ₁ (1)

The forward voltage V of the conversion diode 2 is given by

ViJLL- _log J- + Vs ....... (2)

^{q 1}

here mean:

Vs: terminal voltage of conversion diode 2 at current i i: reference current

K: Boltzmann constant

T: absolute temperature, and

q: electrical charge of an electron.

When the conversion diodes 2 and 3 are the same, the voltage is Va given by at the connection point a_

Va m 2. (^ E.. Log. - ~ ■ + Vs) (3)

l> as means that Va is directly proportional to the size of the APEX Display for the brightness value or luminance value (Bv) of the zu object to be photographed.

Similarly, that by the conversion diodes 8 and 9 is flowing current i given by

^R 2

where V is the terminal voltage of resistor 7 and R is Resistance value.

The voltage Vb at the connection point b_ between these parts

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_ 7 -

is, as in equation (3), given by

Vb 2. (-. Log -— + Vs) (5).

As mentioned above, the operational amplifier 14 is a switching arrangement designed and is reversed or switched when the terminal voltage at the non-reversible input is the same the terminal voltage at the reversible input. Hereinafter should these terms be used: t_ is the period of time from the opening of the reset switch 12 to the Time is required at which the operational amplifier 14 is switched; i_ is the electric current of the constant current source 13; Co the capacitance of the integration capacitor 11; and Vo is the terminal voltage of the capacitor 11 when the amplifier 14 is switched; using equations (3,5) one can write:

Vo m Va - Vb = 2. £ - ^. log -A- (6),

^q 2

it m Co. Vo. (7).

The equations (6) and (7) then result in:

t = (2f ~). 2 .If log - ^ (8)

because in this circuit V _{1 is} almost equal to V_ (V ■ V_), the following can be written with the aid of equations (1) and (4):

With the help of this relationship, equation (8) can be transformed to Co _ _ R,

Here R is the resistance value of the photoconductive element 1, which changes with the brightness of the object; the resistance

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The value of the resistor 7 changes with the shutter speed or exposure time and film speed; then, R and R can be represented by the following equations, respectively will:

mean:

^R 2 - ^Y mean:

Bv

■ do)

Bv

: Constant of proportionality: photo-resistance ratio of the photoconductive Element

: Brightness value or luminance value of the object in the APEX system

2 ^ 2 ( ^Tv - ^Sy ) (11);

: Proportionality constant: resistance ratio

: The value for the shutter speed or the time value in the APEX system;

: The value for the image sensitivity or the speed value in the APEX system.

Tv

Sv

If one assumes that if * % = ^ ', one can write with the help of the equations (9,10,11):

Co

T .T

where K '« Yi / log 10

y (Bv + Sv- Tv)

Assuming that Y - 0.5, then:

q I

^: 2 + (Bv ₊ Sv-Tv) / (12).

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Co, i, Κ ■, T and q are predetermined values, while Y and K are determined by setting.

If Av is the aperture value in the APEX system represents, then the following equation applies in the APEX system: Av = Bv + Sv-Tv; then equation (12) can be transformed to

t = K (Ko + Av). . (13).

Since Ko and K are proportionality constants, Equation (13) represents the proportional relationship between the time t and the value Av of the APEX system, i.e., time lags linearly advances or extends linearly when the diaphragm or iris is moved forward by one step. That is, if the Lens from the f-number 1.4 to the f-number 22 (8 steps), 8 ms are sufficient for these 8 steps.

The constant Ko serves as a Bezuaswert that the time t_ with the F-stop value Av connect ^; however, the value can be changed by corresponding Choosing R and R (from equations 10 and 11) adjusted so that it is useful when assembling the mechanism.

In Fig. 2 an apparatus is shown in the present Invention can be used; a retaining ring 20 is used to hold an aperture plate 21, for example an iris diaphragm; the retaining ring 20 is attached to a lens mount (not shown) and provided with a hole 20a, which receives a pin 22; the pin 22 serves as the axis of rotation for the aperture plate 21. The aperture plate 21 has a further pin 24, which is in a TTutbereich 23a in a Ring 23 is received, which is used to open and close the shutter; this closes the diaphragm of the iris diaphragm, when the ring 23 is rotated clockwise as shown in FIG. The ring 23 for opening and closing

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the diaphragm is formed at one end with a gear or drive portion 23b which is connected to a group of regulator mechanisms 25 is connected. Furthermore, the drive area 23b has an arm 23c which extends in the direction of the camera housing extends and ends under the front end 28a of a pivot lever 28 for the panel. The aperture plate 21 is on the position "Open" set until the arm 23c makes contact with the front End '28a comes, which is held against a stop 31 by a spring 33. A spring 26 serves as a drive source, around the ring 23 for opening and closing the shutter in a clockwise direction to rotate, whereby the aperture leaf is "closed".

An electromagnet is provided with the reference number 15; the reference number 27 denotes a pawl for the ring which is used to open and close the shutter; the front end 27a of the The pawl is in engagement with a ratchet wheel 25a which forms the actuator of the group of control mechanisms 25; the other End 27b cooperates with the electromagnet 15, this end forming an extension of the armature during excitation.

A drive lever 29 for the diaphragm is elastically coupled to the pivot lever 28 for the diaphragm by means of a spring 33; the spring 33 is more powerful than the spring 26, or more Before the shutter release 30 is a pawl 30a of a stop plate with one end of the operating lever 29a A _n for the shutter in engagement-, to thereby stop the lever aperture. The pivot lever 28 has a pin 28d, the surface of which is covered with an insulating material and which is fixedly attached to the other end 28c to operate the reverse switch 12 for the capacitor 11; the drive lever 29 has a pin. 29c, which is also covered with an insulating material; the pin 29c is fixedly attached to the drive lever 29 to operate the memory switch 4.

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When a trigger plate 32 is moved by hand in a direction indicated by the arrow in FIG. 2, depresses Arm 32a of the plate 32 a pin 30b on the stop lever 30, to rotate the lever 30 clockwise; that is how the Drive lever 29 out of engagement. The drive lever 29 can now move counterclockwise under the action of the spring 34 Turn to open memory switch 4. A pin 29b then presses against a cam surface 28b of the pivot lever 28 to thereby rotate the pivot lever 28 counterclockwise. At the beginning, the pin 29b is in a suitable manner in Maintained distance from the cam surface 28c, so that the opening of the switch 4 during this period in the correct Timing or coordination takes place.

As soon as the pivot lever 28 begins to rotate, the reset switch 12 is opened in order to initiate the operational sequence of the circuit described above. The ring 23 for opening and closing the shutter and the gear portion 23b begin their clockwise rotation by means of the spring 26, while the ratchet wheel 25a of the regulator portion 25 rotates counterclockwise. After the lapse of the time t_, when the amplifier 14 switches over, the electromagnet 15 is de-energized and the ratchet wheel 25a is stopped in that the front end 27a comes into engagement by the action of the spring 35; in this way the opening movement of the ring " ¹ 23" is ended and an aperture value is fixed.

Although it is not shown in the figures, the drive lever 29 and the pawl 27 can after actuation to the in Fig. 2 position shown are returned when the film is wound or further wound; as an alternative to this can also an express return will take place.

Although in the embodiment described above, the memory

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switch 4 opened by the drive lever 29 for the diaphragm has been, it can also be opened and closed by the trigger plate 32, because it only needs to be ensured that the switch just before moving the aperture stop 21 (or moving a mirror up if a camera used with a mirror).

Furthermore, the time delay of the electromagnet (the time from the inversion of the amplifier 14 to the Time at which the armature 27b disengages) and the actuation delay of the mechanisms are electrically controlled .

As can be seen from the above description, the diaphragm value Av and the time £ (the period of time from the opening of the reset switch 12 to the inversion of the amplifier 14) in a linear relationship to. each other so that the time is significantly reduced required to adjust the aperture.

Since the brightness value of the object can also be stored, the device described here can be used with single-lens reflex cameras in which the incidence of light is interrupted while the shutter is released. After all, the Control of the aperture by the electromagnet without measuring devices or similar elements, so that the device can be installed in compact form in the camera housing or the lens barrel.

Claims

609817/083 1 -13-

Claims (10)

Claims h ./A method for automatic exposure control for a camera with a lens system, a film transport system that contains a film with a certain film speed, with a shutter system that opens and closes the shutter with a variable shutter speed, with a movable diaphragm for determining the area of the lens system during the operation of the shutter, and with a light measuring arrangement for measuring the brightness of the object of the camera, the diaphragm being controlled by means of the light measuring arrangement in such a way that, after the start of the movement of the diaphragm, the light measuring arrangement automatically detects the movement of the diaphragm in the appropriate position Position for the correct film exposure depending on the film speed, the shutter speed and the brightness of the object, characterized in that a linear relationship is established between the value for the brightness of the object and the time span from the beginning of the movement of the shutter de (21) is required until the end of this movement. 2. The method according to claim 1, characterized in that the brightness of the object with the film sensitivity and the Shutter speed is compared electronically to control the point in time at which the shutter (21) stops closing. 3. Device for automatic exposure control in one -14- 609817/0831 single-lens reflex camera with a movable aperture, with a shutter with variable shutter speeds, and with a film transport system containing a film of known film speed, characterized by a measuring device (i) for the brightness of the camera object, by a storage arrangement for the object brightness, to order before the start of the diaphragm movement to store a minimum brightness value for the camera object by a determination device for the aperture value, which the aperture (21) of the camera with; at a previously set speed a locking device to stop the movement of the diaphragm (21) and the position on receipt of an external control signal to fix the diaphragm (21), and by a timer that is triggered when the diaphragm (21) begins to move, in order to supply the locking device with the external control signal in such a way that the brightness value is in a linear relationship at the time between the start of the movement of the shutter (21) and the external control signal for the locking device stands. 4. Apparatus according to claim 3, characterized in that the measuring device for the object brightness is a light-sensitive Resistance (1) is. 5. Device according to one of claims 3 or 4 _t, characterized in that the memory arrangement is an electronic switching 609817/0831 tion is. 6. Apparatus according to claim 5, characterized in that the electronic circuit has a storage capacitor (5), the diodes (2, 3) performing a logarithmic conversion are connected in parallel and can be connected to them in a switchable manner is, wherein the diodes (2,3) are in series with the measuring device (i) for the object brightness. 7. Device according to one of claims 3 to 6, characterized in that that the determination sionidltuqg for the aperture value has a mechanical control device (25). 8. Device according to one of claims 3 to 7, characterized in that the locking device is a locking pawl (27), an operable from the locking pawl (27) electromagnets (15) and into connection with the BestimmungseJnricl ± ung ** ^aperture value actuatable Ratchet wheel (25a) has in order to stop the determination when the electromagnet (15) is excited. . ,; 9. Device according to one of claims 3 to 8, characterized in that that the timer is an electronic timer. 10. Apparatus according to claim 9, characterized in that the -16- 609817/0831 25U660 electronic timing circuit an integration capacitor (ii) having connected in series with a constant current source (13) is, with a reset switch (i2) in parallel with the Capacitor (11) is connected. . Device according to one of Claims 3 to 10, characterized in that that the diaphragm is an iris diaphragm (21). 60 9 817/0831